havent done much long stuff recently but this is just my opinion
- read more - pay attention to devices and phrases that you like and want to use for yourself
- just write - its cliche advice but similar to visual art, you can't reasonably expect your work to live up to your own expectations right away - better to get things down, accumulate experience, and come back to it later with fresh eyes. writing is an iterative process. this includes being willing to take a break from your main story sometimes and trying to write other things to expand your perspective